Gary Oldman
as Winston Churchill

Kristin Scott Thomas
as Clemmie

Ben Mendelsohn
as King George VI

Lily James
as Elizabeth Layton

Ronald Pickup
as Neville Chamberlain

Stephen Dillane
as Viscount Halifax

Nicholas Jones
as Sir John Simon

Samuel West
as Sir Anthony Eden

David Schofield
as Clement Atlee

Richard Lumsden
as General Ismay

Malcolm Storry
as General Ironside

Hilton McRae
as Arthur Greenwood

Benjamin Whitrow
as Sir Samuel Hoare

Joe Armstrong
as John Evans

Adrian Rawlins
as Air Chief Marshal Dowding

David Bamber
as Admiral Ramsay

Paul Leonard
as Admiral Dudley Pound

David Strathairn
as President Roosevelt (voice)

Eric MacLennan
as Tom Leonard

Philip Martin Brown
as Sawyers

Demetri Goritsas
as Cabinet Secretary Bridges

Jordan Waller
as Randolph Churchill

Alex Clatworthy
as Diana Churchill

Mary Antony
as Mary Churchill

Bethany Muir
as Sarah Churchill

Anna Burnett
as Pamela Churchill

Jeremy Child
as Lord Stanhope

Brian Pettifer
as Lord Kingsley Wood

Michael Gould
as Lord Londonderry

Paul Ridley
as House of Commons Speaker

Robin Pearce
as Ernle Hastings

Michael Bott
as Equerry

Olivier Broche
as Reynaud

Mario Hacquard
as Daladier

Pip Torrens
as BBC Producer

Edmund Wiseman
as Actor

Hannah Steele
as Abigail Walker

Nia Gwynne
as Alice Simpson

Ade Dee Haastrup
as Marcus Peters

James Eeles
as Maurice Baker

Flora Nicholson
as Jessie Sutton

Bronte Carmichael
as Young Girl on Tube

Roisin O'Neill
as Agnes Dillon

John Locke
as Oliver Wilson

Joanna Neary
as Margaret Jerome

Richard Glover
as Brigadier Nicholson

Tom Ashley
as Ramsay Staffer

Joshua Higgott
as Reporter

Imogen King
as Teenage Girl at Tube Map

Miles Gallant
as Naval Map-Room Officer

Faye Marsay
as Sybil

John Atterbury
as Sir Alexander Cadogan

James Harkness
as AD Nicholl (Secretary #1)

Joshua James
as W D Wilkinson (Secretary #2)

Charley Palmer Rothwell
as Christopher Wilson (Photographer)

Patsy Ferran
as Maid

Sarah Flind
as Cook

Steffan Donnelly
as Back Bencher

Kieran Buckeridge
as Cecil Beaton

Johnny Otto
as Member of Parliament (uncredited)